Circuit breaker operating mechanism



Feb. 19, 1952 J. K. HODNETTE ET AL CIRCUIT BREAKER OPERATING MECHANISM 2SHEETS-SHEET l Filed July 5, 1947 .m um

INVENTORS .Zahn A. Hadnve and WITNESSES:

Feb 19, 1952 J. K. HoDNl-:TTE ET A1.

CIRCUIT BREAKER OPERATING MECHANISM Filed July 5, 1947 2 SHEETS--SHEET 2WITNESSES:

ATTORN Patented Feb. 19, 1952 CIRCUIT BREAKER OPERATING MEoHANIsM JohnK. Hodnette and Merrill G. Leonard, Sharon, Pa., assignors toWestinghouse Electric Corporation, East Pitt tion of Pennsylvaniasburgh, Pa., a corpora- Application July 5, 1947, Serial No. 759,272Claims. (Cl. 20G-116) This invention relates to circuit breakers, andmore particularly, to operating and tripping mechanism therefor.

Certain features disclosed but not claimed in this application are fullydisclosed and claimed in copending divisional applications, Serial No.240,875 and Serial No. 240,876, filed August 8, 1951, by John K.Hodnette and Merrill G. Leonard, and assigned to the assignee of thisapplication.

One object of the invention is to provide a circuit breaker embodying animproved operating mechanism wherein the load of the main operatingspring is not imposed on the breaker latch.

Another object' of the invention is to provide a circuit breakerembodying a trip member controlled by a thermal trip element to trip the'breaker and to effect an indication of the condition of the breaker,and an indicating trip member controlled by said thermal trip element toeffect an indication of the approach of a dangerous circuit condition.

Another object of the invention is to provide a circuit breakerembodying a; trip member controlled by a thermalA trip element to tripthe breaker and to eiiect an indication of the condition of the breaker,an indicating trip member controlled by said thermal trip element toeffect an indication of the approach of a dangerous circuit conditionand means operatively relating the operating mechanism of the breakerandy the indicating trip member to permit resettingV of said indicatingtrip member without disturbing the breaker contact position.

Another object of the invention is to provide a circuit breakerembodying a thermal trip device responsive to overload current to tripthe breaker and an auxiliary thermal element responsive to ambienttemperatures to control the thermal trip device to trip the breakerafter a relatively long time delay when the ambient temperature is lowand after a relatively short time delay when the ambient temperature ishigh.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to structure and operation, together withadditional objects and advantages thereof, will best be understood fromthe following detailed description thereof when read in conjunction withthe accompanying drawings.

In said drawings:

Figure l is an elevational sectional view taken along line I-I of Fig. 2showing a circuit breaker be more fully described hereinafter.

2 embodying the principles of the invention, the breaker being shown inthe closed position,

Fig. 2 is a sectional view taken on line II--II of Fig. l and looking inthe direction of the arrows,

Fig. 3 is an elevational view similar to Fig. 1 but showing the breakerin the tripped open position, and

Fig. 4 is an elevational view similar to Fig. 1 but showing the parts inthe reset position.

Referring to Fig. l of the drawings, the circuit breaker comprises abase I'I of insulating material on which is mounted the breaker contactstructure, a metal housing I3 secured to the base II, an operatingmechanism indicated generally at I 5 and a trip device indicatedgenerally at I1.

The contact structure comprises a main stationary contact I9 rigidlymounted on the inner end of a rod 2I slidably mounted in the base II. Acoil spring 23 surrounds the rod 2| and is compressed between the baseII and a connector 25 secured to the rod 2I and to the contact I9 toprovide contact pressure. A limit nut 21 .is threadedly mounted on therod 2I outside the base II. A cooperating movable contact 2i is rigidlymounted on a channel-shaped switch arm 3| pivotally mounted on a p-ivotpin 33 supported in a U-shaped bracket 35. The bracket is secured to thebase II by means of a screw 3l.

The contact structure also comprises a stationary arcing contact 39rigidly mounted on a conducting support member 4I' secured by means of ascrew 43 to the base II. and a cooperating movable arcing contact 45.The movable arcing contact 45 is rigidly mounted on a channelshapedswitch member 41 which stra'idles the switch arm 3I and is pivoted onthe pivot pin 33. A compression spring 49 disposed between an extension5I of the main switch arm 3I and the yoke portion 53 of the arcingContact switch arm 41 provides contact pressure for the arcing contacts39-45 and also maintains the arcing contacts in closed position untilafter the main contacts I9-29 have separated on an opening operation.

The operating mechanism I5 is supported in a generally U-shaped frame 55the bight 57 of which is rigidly secured to the housing I3. Theoperating mechanism comprises a releasable member or carrier 59pivotally mounted on a xed pivot pin 6I mounted in the side members ofthe frameV 55. The carrier 59 has a latch portion 63 adapted to engagealatch member 65 forming part of the trip mechanism which will Thecarrier 59 is biased in a clockwise direction by means of a spring 61which surrounds a. spring guide 69 pivotally connected at one end bymeans of a pivot pin 1| to the carrier. The spring 61 is compressedbetween a shoulder on the spring guide 69 and a rod 13 mounted on andextending between the side members of the frame 55. The carrier 59 isoperatively connected to the switch arm 3|y by means of a togglecomprising toggleA jects beyond the side members of the switch arm 3|and through elongated slots 05 (only one being shown) in the sidemembers of the arcing contact switch arm 41. v

An actuator comprising a pair of spaced actuating levers 91 is providedfor operating the toggle 15-11 to manually open and close the contacts.The actuating levers 91 are disposed adjacent the inner sides of theU-shaped frame 55 and each of the levers carries a pivot pin 89 which isseated in a slot 9| in the adjacent frame. The actuating levers 01 arerigidly joined by an integral cross member 93 and each of the levers 81is provided with a hook portion 95 which in the closed position of themechanism engages an end of the knee pivot pin 19 to hold the toggle15-11 in a slightly underset position to thereby hold the switch arms 3|and 41 in the closed contact position.

A pair of overcenter springs 91 is provided to operate the levers 81 andtherethrough the toggle if 1511 in order to manually open and close thecircuit breaker. The springs 91 have one end hooked over laterallyprojecting ears 99 on the levers 81 and the other ends of the springsare hooked over an operating rod extending through guide slots |03disposed in parallel alignment in the frame members 55. Secured to ashaft for rotation therewith is a pair of operating arms |01 each havingits free end bifurcated to embrace the rod |0| adjacent the endsthereof. The shaft |09 is pivotally supported in plates |09 secured tothe outside of the housing I3 and provided with mounting feet I Iwhereby the circuit breaker may be mounted on a suitable support (notshown). One end-of the shaft |05 extends to the outside of the housingand has secured thereto an operating handle indicated at ||3 (Fig. 2)for manually operating the shaft |05 and the arms |01.

The circuit breaker may be opened manually by rotating the handle ||3and consequently the shaft |05 and arms |01 approximately 90 in acounter-clockwise direction from the position shown in Fig. 1. Duringthis movement the arms |01 cause the rod |9| to move upwardly in theslots |03 carrying therewith the vends of the springs 91 attachedthereto. When the rod |05 moves the line of action of the springs |01overcenter above the pivot 89 of the levers 81, they bias the actuatorlevers 81 in a clockwise direction. Continued movement o'f the arms |01and the rod |9| increases the biasing force until a point is reachedwhen the's'prings rotate the actuating levers 81 clockwise about thepivots 89. In 'the closed and latched position of the'circuit breaker,the pivot 83 connecting the toggle link 11 to the releasable carrier 59is in axial alignment with the pivot 89 of the actuating lever 81 andthe knee pivot pin 19 remains in engagement with the hook 95,consequently, the toggle link 11 and the lever 81 will move as a unitduring manual opening operation. The clockwise movement of the actuatorlever 31, therefore, causes collapse of the toggle 15--11 and opening ofthe contacts. During the opening movement of the mechanism the switcharm 3| is nrst moved in a counterclockwise or opening direction to openthe main contacts lil-29 while the spring 49 maintains the arcingcontacts 39-45 closed until after the main contacts have separated.Shortly after the main contacts have separated, the pin 8| engages theouter end of the slot 85 in the switch arm 41 and thereafter moves bothswitch arms 3|-41 to the full open position in unison in which positionthe parts are shown in Fig. 4. f

The contacts are closed by rotating the shaft |05 and the arms |01clockwise from the Fig. 4 position to the position in which they appearin Fig. 1. During this movement the arms |01 carry the rod |0| therewithmoving the line of action of the springs 91 over center below thealigned pivots 83-89, whereupon the springs 91 bias the actuating lever81 in a counterclockwise direction, and, since the knee pin 19 of thetoggle 15-11 is in engagement with the hook 95, the toggle is biasedtoits underset position. Continued clockwise movement of the arms |01increases the spring bias on the actuating lever 81 and the toggle untila point is reached where the springs 91 suddenly straightens the toggle1511 and closes the contact with a snap action.

The configuration of the slot |03 is substantial-r ly concentric withthe ears 99 on the actuating levers 81 so the slot controls the springs91 so as to produce as little change as possible in. the length of theover center springs 91 until the toggle is broken, thereby reducing theenergy required to operate the breaker. As will be more fully broughtout later, the shape of the slots |03 also control the operation of areset lever.

The circuit breaker may be tripped open automatically by operation ofthe trip device l1 in response to overload currents. The trip devicecomprises a base ||5 of insulating material secured to the housing I3, acover ||1 also of insulating material secured to the base ||5 by meansof rivets ||9 (only one being shown), a biased member |2| releasable t0actuate the latch 55 and a tripping bimetal element |23 which isoperable to release the member |2 l. The bimetal element is secured atone end to a metal bracket |24 supported on insulating plate |25 mountedon the base ||5 and at the other end carries an insulating block |21 towhich is secured a metal latch |29. A connector |3| is electricallyconnected to the free end of then bimetal element and a iiexibleterminal conductor |33 is connected to the connector. The nexibleconductor |33 extends to the left and is supported on a bracket |35mounted on the base ||5. Thereafter the conductor |33 extends outthrough an opening in the cover ||1 where it serves to connect thebreaker in an electrical circuit.` The bracket'l24,` and hence, theiixed end of the bimetal element is connected by means of a ilexibleconductor |31 to the switch arms 3| and 41, the conductor |31 extendingdownwardly through an opening in the base where it is mechanically andelectrically secured to a connector |39, and to the switch arms 3| and41. The connector |39 provides a point where a terminal strip |40 may beconnected to provide a third terminal between the bimetal and thecontrols. The main stationary contact I9 is connected by means of aflexible conductor l4| to the stationary arcing contact 39 and thecircuit through the breaker is completed by means of a flexible terminalconductor |43 also connected to the fixed arcing contact 39 andextending out through an opening in the base l. An auxiliary bimetalelement |45, disposed above the tripping bimetal |23 but insulatedtherefrom by a strip |41 of insulating material, is Xedly mounted at itsleft-hand end and adapted to deflect, when heated, in the same directionas the tripping bimetal |23.

The releasable member |2| is pivotally mounted at 49 on an adjusting armi5! which, in turn, is pivotally mounted on a pivot pin |53 which issupported in a suitable opening in the base ||5. The pivot |49,adjusting cam |5| and pivot pin |53 are directly behind pivot |89, asecond adjusting cam |9|, and pivot pin |43, as hereinafter described.The member |2| is biased by means of a spring |55 in a clockwise ortripping direction. The spring |55 has one end hooked into an opening inthe member |2| and the other end anchored to the free end of theadjusting arms |5|. Secured to the adjusting arm 15| at a point adjacentits free end is a rod |51 (Fig. 2) which extends upwardly through anenlarged opening in the base t5 and has its upper end threaded toreceive an adjusting nut |59. A spring |6| coiled about the rod |51 andcompressed between the bottom surface of the base ||5 and a washer |53biases the free end of the arm |5| downwardly. By turning the nut |59 inone direction the rod |51 may be moved upwardly rotating the arm |5| ina counterclockwise direction. Turning the nut |59 in the oppositedirection permits the spring |9| to lower the rod |51 and rotate the arm|5| in a clock,- wise direction. Since the releasable member |2| ispivotally supported at |49 on the arm |5!, it

will be thus moved up or down relative to the latch |29 to thereby varythe overlap of the member |2| with the latch.

The latch member 65 is U-shaped and the two legs thereof are mounted ona shaft |55 for movement therewith, the shaft |95 being mounted forrotation in openings in the side members of the frame 55, The yokeportion |61 of the latch member is shaped inwardly to form a latchportion |99 which engages the latch portion 63 of the carrier 59 tonormally restrain the latter in the position shown in Fig. l.

The bimetal element |23 has its high-expansion side facingI downwardlyso that, when heated a predetermined amount in response tc overloadcurrents, the bimetal element |23 will deflect upwardly to disengage thelatch |29 from the releasable member |2|. When this occurs, the spring|55 rotates the member 2| clockwise about its pivot |49 and the lowerend |1| thereof strikes the latch member 65 a blow to disengage thelatch portion |69 thereof from the latch portion 63 of the carrier 59thereby releasing the carrier. Upon release of the carrier 59, thespring S1 rotates the carrier in a clockwise direction about its pivot5| to the position in which it appears in Fig. 3, thus moving the switchmembers 3| and 41 to the open -position. During the early portion ofthis movement the knee pin 19 of the toggle 15-19 moves out of the hookportion 95 of the actuator levers 81 and shortly thereafter the end ofthe spring 'P guide 69 strikes the toggle link 11. This action causescollapse of the toggle and rotates the toggle link 11 clockwise aboutits pivot 83 to eifect movement of the switch arms SI-A'i to the openposition. The mechanism is shown in Fig. 3 in the tripped open position.

During the automatic opening operation, the knee pivot pin 19, aspreviously set forth, escapes from the actuating levers 81 and beforethe breaker can be reclosed it is necessary to reengage the actuatinglevers with the knee pin 19 and also to reset and relatch the carrier59. Both of these operations are accomplished by moving the rod |0|upwardly in the slots |03 from the Fig. 3 position to the position shownin Fig. 4. This is done byV rotating the shaft |05 and the arms |01 ina, counterclockwise direction as far as they will go, the movement ofthe rod being limited by engagement with the upper end of the slot |03.During this movement the rod |0| carries the line of action of thesprings 91 over center above the pivot 89 (Fig. 3) of the levers 81whereupon the springs 91 actuate the levers in a clockwise directionuntil they engage the knee pin 19. Next in its upward travel, the rodI0| engages a projection |13 on the carrier 59 and rotates the carriercounterclockwise about its pivot 6 Near the end of this movement of thecarrier 59 the latching end thereof Wipes by the latch portion |69 ofthe latch member which is then restored clockwise to latching positionby means ,of a spring |15, the clockwise movement of the latch 65 beinglimited by engagement with the frame 55. During the counterclockwisemovement of the carrier 59 the pivot 83 for the toggle link 11 movesback slightly beyond the normal position in which it is aligned with thepivot 89 of the levers 81. This movement thrusts the knee pin 19 intothe hook portion of the levers 81, and provides a slight overthrow forthe latching portion 63 of the carrier beyond latched position.

The rod |0| in its upward travel, next engages a cam surface |11 in onewall of a slot |19 in a resetting lever |8| which is pivotally mountedon the pivot pin 6 I, and in cooperation with the slots |03, moves thislever counterclockwise about its pivot. During this movement, an ear 93(Figs. 2 and 4) formed at right angles to the upper end of the resettinglever engages the releasable tripping member |2| and rotates itcounterclockwise past its latched position as shown in Fig. 4. The partsare now in the reset position as shown in Fig. 4, in readiness for acontact closing operation which is effected in the previously describedmanner by movement of the arms |01 and the rod |0| in a clockwisedirection to the Fig, 1 posit-ion, during which movement the actuatinglevers 81 acting through the knee pin 19 straightens the toggle 15-11and moves the switch arms to their closed positions. As the rod |0|nears the lower end of its movement, it engages a portion of the slot|19 in the resetting lever I 8| and restores this lever to its initialposition, as shown in Fig. l.

The circuit breaker is designed for use in an oi1 insulated transformer,and it is the purpose of the auxiliary bimetal element |45 to modify thetripping time of the current-carrying tripping bimetal element |23 inaccordance with the temperature ofv the surrounding medium. The bimetalelement |45 is similar to the tripping bimetal |23 and 'also has itshigh-expansion side facing downwardly,Y hence, when heated, will defleetin the same direction as the tripping bimetal |23.

If the transformer temperature rises gradually so that the mass ofcopper, oil insulation, etc., tend to reach their maximum safetemperatures,

vthe auxiliary bimetaI |45, Which is heated by the oil temperature riseand to some extent by conduction and convection from the trippingbimetal |23, will deiiect in the same direction and at approximately thesame rate as the tripping bimetal |23 which is heated by both currentflow and oil temperature rise, hence the bimetal |45 will notappreciably change the trip-time curve of the tripping bimetal |23. Ifthe transformer temperature is low andheavy overload occurs, thetripping bimetal |23 will be' heated rapidly, whereas the temperature ofthe auxiliary bimetal |45 will rise very little and will, therefore,exert a restraining force on the tripping bimetalI23. It will be seen,therefore, that for a given value of overload current, the circuitbreaker will be tripped open after a relatively short time delay whenthe transformer temperature is high and after a relatively long timedelay when the transformer temperature is low. By use of the auxiliarybimetal |45 heavier overloads may be carried for a short time withouttripping, and the'greater temperature rise required to trip on suchoverloads will give faster cooling and thereby the time for resetting isreduced.

The trip-time curve of the trip device may be varied by substitutingbimetal elements having different characteristics for the auxiliarybimetal element, by varying the space between the tripping bimetal andthe auxiliary bimetal and by varying the thermal insulation between andaround the bimetal elements and also by varying the characteristics ofthe tripping bimetal.

Means is provided for indicating a partial overload condition which isnot of sufficient magnitude to trip the breaker open but which indicatesthat the current in the circuit is approaching a dangerous overloadcondition or that a dangerous overload condition has been approached andthen cleared itself without tripping thebreaker, also to indicate thatthe breaker has been tripped open in response to a dangerous overloadcondition.

The indicating mechanism comprises a releasable member |81 (Figs. 1 and2) pivotally supi ported by means of a pivot pin |89 on an adjustinglever |9|. The lever |9| is pivotally mounted on the pivot pin |53 whichsupports the lever on the base ||5 of the trip device. A spring |95having one end hooked in an opening in one arm of the releasable member|81 and the other end hooked in an opening in the lever |9| biases themember |81 in a clockwise direction about its pivot |49. The member |81is normally restrained against clockwise movement by engagement with thelatch |29. An adjusting rod |91 (Fig. l), similar to the rod |51 (Fig.2) for the lever |5I, is secured to the lever |9| at a point near itsfree end and extends upwardly through 'an opening in the base ||5. Theupper end of the rod |91 is threaded to receive an adjusting nut |99 anda compression spring 20| coiled about the rod |91 is disposed betweenthe base ||5 and a washer 203 bearing against the lever |0|. By thismeans the lever [9| can be moved up and down about its pivot |93 tothereby shift the pivot |89 for the member |81 and vary the amount ofoverlap between the member |81 and the latch |29. rThe member |81 isadjusted to be released by the latch |29 before the bimetal element |23deflects far enough to release the member |2| to trip the breaker. Thereleasable member |81 is electrically connected by means of a .nexibleconductor 205 to a conductor 201 extending transversely through thebreaker and secured to the base |I5 of the trip device. The member |81is made of conducting material and carries a stud or contact 209 also ofconducting material which, upon release and clockwise movement of themember |81 is adapted to make butt engagement with the end of a fixedcontact 2|| to thereby close an electrical circuit and energize anindication device (not shown) but preferably a signal light to givevisual indication.

The releasable trip member |2| is also electrically connected by meansof a exible conductor 2|3 to the conductor 201 and carries a contact 2|5which, upon release of the member to effect tripping of the breaker,engages the end of a xed contact 2 |1 directly behind the xed contact2|| and closes an electrical circuit to energize an indicating device.The fixed contacts 2| and 2|1 may be connected together and connected ina circuit (not shown) to energize a single indicator or they may beconnected in separate circuits to energize separate indicators. Thereturn circuit (not shown) from the indicators is connected to a supplyconductor 2|9 also secured to the base ||5 but insulated from the supplycircuit 201. The supply conductors 201 and 2|9 extend outside of thehousing I3 (Fig. 2) to be connected to a supply circuit, or to beconnected to similar conductors in another circuit breaker assembledadjacent the first breaker in a manner to be more fully described later.

As previously stated, the releasable signal member |81 is adjusted bymeans of the lever I9| and the adjusting rod |91 (Figs. 1 and 2) to tripand close the circuit to the indicator before the releasable trip member|2| is released to trip the breaker. Hence, if an overload currentoccurs which approaches a dangerous value and trips the signal member|81, but which is cleared before it releases the trip member |2 I, themember |81 will close its circuit and energize the indicating means.Under this circumstance, it is desirable to reset the member |81 Withoutopening or otherwise disturbing the main breaker contacts. This isaccomplished by a partial stroke of the arms |01 and the rod 10| inopening direction which is elfected by a partial opening stroke of thehandle ||3 (Fig. 2). During this partial stroke, the rod |0| engages thecam portion |85 of the resetting member |8| and rotates this member in aclockwise direction from its Fig. l position causing an ear 22| on themember |8| to engage an arm 223 on the member |81 to rock the latter ina counterclockwise or resetting direction to its relatched position asshown in Fig. l. After the release signal member |81 is relatched, thearms |01 and the rod |0| are restored clockwise to their normalpositions and since the rod |0| was not moved far enough to carry thesprings 91 over center, the main contacts remain in their closedposition. If a single indicating device is utilized which is energizedby both the releasable member |2| and |81 with their contactselectrically connected in parallel, and this indicator remains energizedafter the member |81 has been reset, it indicates that the breaker hasbeen tripped open and must be reset and reclosed. However, with twoindicators operated independently by the member |81 and the trip member|2I, a single energized indicator would inform the attendant that anoverload had occurred but had cleared without tripping the breaker, inwhich event it would only be necessary to reset the member |81 withoutopening the breaker. If both invposition of the breaker contacts.

9 dicators were energized the attendant would know immediately thebreaker was tripped open and must be reset and then reclosed.

As previously stated, two or more circuit breakers may be assembled andtied together for unitary operation to control a multi-phase circuit.While only a single circuit breaker has been described, the breakers tobe assembled are identical, hence, oniy the meansfor providing unitaryoperation of two or more circuit breakers will be described. When two ormore breakers are assembled togetherythe plates m9 together with themounting feet are omitted except those on the outside of the endbreakersand the'break- -ersare secured together Iby means of a pluralityof bolts 225 (Figs. 1 and 2) passing through all oi i the .assembledbreakers-and h'avingnuts 221 fthreadedlyengaging the endsthereof.1 Thetrip -shafts |65 and the vlatch-members 65 are-tied'together for unitarymovement by means of a sleeve 229 (Fig. 2) which couples the shafts |65so that a tripping operation of the latch member 65 for one of thebreakers in response to an overload current occurring in the relatedphase circuit will operate the latch members for all of the breakers.The operating shaft |95 described for the single pele breaker isreplaced by a similar shaft E3| (Fig. 2) which extends through all ofthe breakers and has secured thereto for movement therewith theoperating arms |551 for each breaker. Operation of the shaft 23| willeffect manual opening and closing of the contacts of all of thebreakers, reset and relatch the mechanism and reclose the contacts ofall the breakers in the same manner as was described for the single poleunit.

The supply conductor 2631 for the indicator device of each phase breakeris provided at one end with a spring clip 233 (Fig. 2) for releasablyreceiving the externally projecting end of the conductor of the adjacentphase breaker so that the supply circuit extends through all of thebreakers. The supply conductors 2|9 are grounded to their respectivemetallic housings.

From the foregoing description, it will be apparent that there isprovided a circuit breaker embodying a tripping mechanism controlled bya thermally responsive element for opening the breaker contacts undercertain overload current or temperature conditions and for effecting anindication of the condition of the breaker operating mechanism. There isalso provided a second trip mechanism controlled by the thermallyresponsive element for eiecting an indication of the approach of adangerous overload or temperature condition of a lesser magnitude thanthat required to trip the breaker, The arrangement of the tripmechanisms being such that in the event the condition which causedoperation of the second trip mechanism disappears without having trippedthe breaker, the trip mechanism may be reset by partial operation of thebreaker operating mechanism without disturbing the There is alsoprovided independent adjusting means for adjusting the trip mechanism tovary the amount of overload current required to trip the breaker and forindependently adjusting indicating trip v mechanism to vary the amountof overload and/or temperature rise required to eect an indicationwithout tripping the breaker.

Having described the invention in accordance with the patent statutes,it is to beV understood that various changes and modifications may bemade in the structural details thereof without 'l0 departing from someofthe essential features o the invention.

We claim as our invention:

1. In a circuit breaker comprising relatively movable contacts,operating mechanism yfor said contacts comprising a manually operablemember, an actuating member, an overcenter spring operable by saidmanually operable member to operate said actuating member, cam means forcontrolling the tension of said overcenter spring during an operationthereof, a toggle normally engaging the actuating member and operablethereby to open and close said contacts, and a trip device operable toeffect operation of said toggle to open said contacts irrespective ofthe position of the manually operable member and said actuating member.

2. In a circuit breaker comprising relatively movable contact means,operating mechanism for said contact means comprising a manuallyoperable member, an actuating member, an overcenter spring operable bysaid manually operable member to operate said actuating member, fixedcam means disposed to effect radial movement of one end of saidovercenter spring relative to said manual operable member during anoperation thereof, a toggle separably engaging said actuating member andoperable thereby to open and close said contact means, and trip meansoperable in response to overload currents to effect operation of saidtoggle independently of said actuating member to cause automatic openingof said contact means.

3. In a circuit breaker comprising relatively movable contacts,operating mechanism for said contacts comprising an actuating member, anovercenter spring having one end connected to said actuating member, amanually operable member related to the other end of said overcenterspring for operating said spring to eiect operation of said actuatingmember, cam means supporting said other end of said overcenter springfor causing movement of said other end of said overcenter springrelative to said manually operable member during an operation to keepthe tension of said overcenter spring substantially constant until itmoves overcenter, a toggle normally engaging said actuating member andoperable thereby to open and close said contacts, and a trip deviceoperable to effect disengagement of said toggle from said operatingmechanism and spring of said contacts irrespective of the position ofsaid actuating member.

4. In a circuit breaker comprising relatively movable contact means,operating mechanism for said contact means comprising an actuatingmember, a manually operable member, an overcenter spring having one endassociated with said manually operable member and the other endconnected to said actuating member, said overcenter spring beingoperable by said manually operable member to operate said actuatingmember, cam means disposed to effect movement of said one end of saidovercenter spring relative to said manually operable member during anoperation thereof to keep said one end of said overcenter spring atsubstantially the same distance from the other end thereof connected tosaid actuating member until it moves overcenter near the end of aclosing operation, a toggle normally engaging said actuating member andoperable thereby to open and close said contact means, said toggle attimes being disengaged from said actuating member to eiect automaticopen- 1 1 ing of said contact means irrespective of the position oi.said actuating member.

5. In a circuit breaker comprising relatively movable contact means,operating mechanisms for said contact means comprising an operatingshaft, manual means for operating said shaft. a pair of spaced arms onsaid shaft, said arms be ing provided with radially extending parallelslots, an actuating member, an overcenter spring said toggleindependently of said actuating member to effect automatic opening ofsaid contacts.

JOHN K. HODNETTE. MERRILL G. LEONARD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,169,586 Leonard Aug. 15, 19392,210,262 Sachs Aug. 6, 1940 2,240,189 Linde et a1. Apr. 29, 19412,284,825 Jennings et al June 2, 1942 2,306,090 Tate Dec. 22, 19422,306,235 Walle Dec. 22, 1942 2,318,279 Aschwanden May 4, 1943 2,501,363Toth Mar. 21, 1950

